Bacteria, Viruses, and Protists

Bacteria Basics

What is the smallest collection of genes (genome) ever found to date?

In 2006, scientists found the smallest collection of genes known (to date): tiny, endosymbiotic bacteria that live inside special cells of a small insect—a sap-feeder, psyllid insect called Pachypsylla venusta. Although it is not uncommon to find bacteria helping out an insect in such a symbiotic relationship, this insect was examined because it had only one species of endosymbiotic bacteria. The researchers sequenced the genome (the complete complement of DNA) for the bacteria Carsonella ruddii, and discovered it was one-third the size of the previously reported “smallest” cellular genome.